1. Field of the Invention
The present invention relates to a diffusive direct reflector manufacturing process, especially to a process of manufacturing diffusive direct reflector by Gray tone exposure, which uses a controllable transmittance Gray tone mask to produce the desired slant changes on a photoresist layer through a one-step exposure process and form the desired diffusive direct reflector.
2. Description of Related Art
FIG. 1 is a schematic diagram of the profile of a perfect diffusive direct reflector. As shown in FIG. 1, ideally, a perfect diffusive direct reflector has a slope with an angle xcex81 on the photoresist layer such that the incident lights r1, r2 can be reflected by the slope in a direction vertical to the lower substrate 10. As such, the reflected lights r1xe2x80x2, r2xe2x80x2 reaching the human eye is the brightest. Further, the bumps on the slope can increase viewing angle due to the adaptive astigmatistic effect on r1xe2x80x2 and r2xe2x80x2. With such a structure, a diffusive direct reflector can meet the display requirements of separating reflective image and surface glare and increasing viewing angle. For meeting the requirements, a two-step exposure process is used as shown in FIG. 2. In FIG. 2, the first-step exposure process produces the slope with the angle xcex81 while the second-step exposure process smoothes the slope produced by the first-step exposure process to control the astigmatistic angle. As shown in FIG. 2, for producing a slant structure in the first-step exposure process, a chromium film photomask as shown in FIG. 3 is used to operate multiple exposures on the photoresist layer. Such a photomask as shown in FIG. 3 must have multiple strip patterns with equal widths and have equal pitches between the strips. In practice, each exposure must shift the photomask a finite distance and produce the slant structure 21 according to increasing or decreasing exposure energy. The increasing or decreasing exposure energy can produce different exposure depth on the photoresist. The finite distance can not only retain previous major exposure depth but also produce an appropriate overlapping area 22 with different exposure depths due to two successive exposures. As such, the slant is formed. At this step, the resulting slant is a ladder profile that cannot control the required astigmatistic angle. In order to control the required astigmatistic angle, using the second-step exposure process forms a smooth profile 23 on each ladder 21 of the slant surface. In the second-step exposure process, any photomask pattern such as circle, triangle, and so on, able to produce 10-30 degrees astigmatistic angle can be used to form a desired slant. However, the complicated exposure procedures take time and cost and may further influence the resulting reflector""s quality. For example, when the required slant is formed closer to a perfect reflector as shown in FIG. 1, the exposure frequency increases in the first-step exposure process and the smoothing profile processing control becomes harder in the second-step exposure process. On the other hand, the lower exposure frequency causes reduced precision and further reduces light efficiency so that the resulting reflector has poor quality.
Accordingly, an object of the invention is to provide a method of manufacturing a diffusive direct reflector using Gray tone exposure, which uses a controllable transmittance photomask to produce the desired slant by a one-step exposure process, thereby simplifying processing, increasing field and saving cost.
Another object of the invention is to provide a method of manufacturing a diffusive direct reflector using Gray tone exposure, which uses a controllable transmittance photomask to form the desired slant and bump by a one-step exposure process so as to control the reflective angle and astigmatistic range of an incident light, thereby increasing the exposure processing productivity.
The method of manufacturing a diffusive direct reflector using Gray tone exposure, comprising the steps: performing the exposure and development processes on a photoresist layer over a substrate using a controllable transmittance photomask pattern. As such, a gradually changing transmittance is obtained by one-step exposure using the photomask pattern and the desired slant is formed. Further, bumps with astigmatistic mechanism can be arranged into the photomask pattern to produce the desired structure with slants and bumps on the photoresist layer at one-step exposure.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.